This invention relates to screen elements for screening apparatus; it further relates to screen decks and screening apparatus provided with such screen elements for screening particulate material, such as ores, minerals and raw materials.
Various types of screen elements have hitherto been proposed, for example in U.S. Pat. No. 3,970,550, wherein wire cables are moulded into ribs on the underside of a screen and protrude from the screen at each edge to be tensioned by devices on the frame of the screen apparatus when in use. U.S. Pat. No. 3,980,555 discloses a wear-resistant screening element of a synthetic plastic material, such as polyurethane, having a plurality of discrete protrusions along all four of its edges to allow the protrusions of adjacent screening elements to be clipped into the same openings in a support frame. A reinforcing grid may be moulded into the screening element.
United Kingdom Pat. No. 1,289,537 shows (screen) plates having a plurality of separate anchoring projections provided on three or four edges of each plate, each projection being shaped to engage and support a reinforcing member in a joint between adjacent plates. The reinforcing member is not moulded into a screen plate during manufacture thereof, but between adjacent plates during assembly of the screen as a whole. United Kingdom Pat. No. 1,485,748 discloses a screening machine including a lattice support frame of polyurethane, each square of the lattice being dimensioned to accept one modular screening element. The support frame has embedded therein a ribbed channel having protruding interrupted projections which engage a complemental undercut in the underside of all four edges of a screen element.
South African Pat. No. 73/7497 discloses a screen having a plurality of interengageable (screening) modules, being clamped together by tensioning rods passing through apertures in each module. Similar disadvantages apply as in the case of U.S. Pat. No. 3,970,550. South African Pat. No. 74/5092 shows screening elements secured to a support means having a plurality of nodule-like securing formations and a similar plurality of complemental formations spaced along all four edges of the screening elements. South African Pat. No. 75/2229 describes screening elements secured around all four edges to frame members, and it has the disadvantages inherent in this mode of fastening, as previously described.
An object of the present invention is to eliminate the disadvantages of existing screen elements and modes of attachment to support frames therefor, as previously described.
Another object is the provision of new, improved and highly effective screen elements and improved means for attachment to and support by support frames, as well as screening apparatus including such screen elements. More particularly, this is achieved by providing screen elements and support frame members therefor, which have a rigid mounting interaction resulting in less sag and distortion of screen elements, easy removal and replacement of any worn or damaged screen elements, joints between adjacent screen elements being protected against entry of particles, a high ratio of apertured area to total screen surface leading to high screen throughput, and particularly advantageous "whip" or "life" of each screen element because of the mode of reinforement coupled to the material of the screen element, also leading to high screen throughput.